Written by Lenny in Friday, May 08, 2009 under
Engineering
Q: I've found that you can't make sound come out of audio speakers by wiring them up to the leads of a guitar through an amplifying op-amp circuit.
I can wire the guitar jack up and plug that into an amplifier, and that works. But how do I power my own speakers?
I resent having my question called naГЇve. Anyone can buy an old amplifier; I'm trying to learn how to build one myself. God knows my university isn't going to teach me something even half as...
A: You can purchase power op-amps from Apex Microtechnology Corporation, 5980 N. Shannon, Road, Tucson, Arizona 85741-5230 or contact them by e-mail ProdLit@TeamApex.com. Their products work well but need careful application (sockets, heat-sinks, by-pass capacitors, etc.) which is explained in their product literature.
From the naivety of your question, it appears to me that you would be better served purchasing a new or used "guitar amp" and connecting that to your...
Comments: 2
with a powerful amplifier.
Your op-amp circuit probably wasn't powerful enough. An opamp without any power transistors to boost it, can put out only a few milliwatts into a 4 ohm speaker.
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Provided your op amp circuit is capable of outputting enough power to drive a speaker, and was correctly made, you may need extra preamplification before it. It may not have enough gain, or is not a match to the guitar's output impedance.
Test it. Turn the gain right up without it connected to the guitar, and touch a finger to the tip of the guitar plug. You should be rewarded with a healthy "blurp". If so, inadequate gain or mismatch could be the problem.
If...